It has long been recognized by physicians and physical therapists that sitting in a conventional chair for long periods of time produces back and muscle complaints as well as discomfort to the stomach and neck. This is brought about by the weight distribution which follows from the 90 degree angle which the body basically must assume when in a conventional sitting position. Persons working at a typewriter or computer console are known to especially suffer in this manner and the condition is obviously aggravated in the case of persons already having back complaints. To solve this problem there have been in use now for some years various embodiments of a therapeutic chair which eliminates the conventional backrest and instead provides a knee rest for the user upon which he may effectively lean forward and have his knees absorb some of his weight, thus relieving the back and spine. Such chairs have found wide use, not only in offices, but in homes as for example, for prolonged watching of television in addition to use by people having back troubles as mentioned above and in particular by pregnant women.
There is substantial prior patent art in this field, of which the following are examples.
U.S. Pat. No. 3,669,493 to Vowles. In addition to the provisions for a chair in the knee rest position, this patent also claims an arcuate support for the feet as an additional feature.
U.S. Pat. No. 4,328,991 to Mengshoel teaches a chair of this type mounted on runners after the manner of a rocking chair, which is an additional claimed feature.
U.S. Pat. No. 4,377,309 to Mengshoel teaches an ankle and knee support element and a storage space for the latter beneath the seat. It also claims variations of ankle supports and is thus distinguished from Vowles above.
U.S. Pat. No. 4,564,237 to Steifensand. This patent teaches a tubular wide frame support of a chair of this type to provide better stability, improved construction and assembly as distinguished from the foregoing.
U.S. Pat. No. 4,589,699 to Dungan. In addition to a separate angular tilting arrangement for the seat and knee rest, this patent covers the feature of a variation in lateral space between the seat and knee rest members as an improvement over the prior art.
A number of design patents have issued covering ornamental features of various emobidments of these chairs indicating their wide adoption.
In actual practice it is often customary to use a conventional chair for a period of time and then switch to a knee rest type of chair to obtain the relief afforded for a while and then switch back to a conventional chair. This, of course, requires having two separate chairs which is cumbersome especially in a business office.
Nowhere does the prior art suggest the construction of a chair which may be readily converted from conventional to therapeutic use as described above or for lounging use.